The broad intent of the proposed collaborative research is to examine the concurrent and long term development effects of varying patterns and qualities of in-home and out-of-home care for infants and toddlers. The site-specific study proposed at the University of Virginia examines the effects of infant child care on children's socioemotional development, and focuses on the predictive role of variation in the stability and quality of children's day care environments. Within this conceptual framework, the timing and extent of day care experience, family environment and background factors (including maternal stress and separation anxiety), and characteristics of the children and examine for their moderating influence on the contribution of day care quality and stability. The research is designed to improve upon methodological weaknesses of prior day care research, to contribute to theoretical issues in this area, and to inform policy debates about infant day care. The study has five specific aims: (1) To assess, prospectively and longitudinally, the socioemotional development of children who have varying child care experiences, including exclusive maternal care, during infancy. A cohort-sequential design is employed in which one cohort of families is first assessed during the third trimester of pregnancy and followed to the child's third birthday, and a second cohort is first seen when the child is 12 months old and followed to age four years. (2) To examine the contribution of variation in the quality of the day care setting to any effects found for early entry into infant day care. We hypothesize that quality of care, rather than "age of entry" into and amount of day care, is the primary predictor of developmental outcomes. (3) To examine variation in the stability of day care as a component of quality. Day care has been studied primarily as a static intervention: one arrangement at one point in a child's life. We propose to examine stability and change in care over time as a predictor of children's adaptation to day care. (4) To examine the interactive effects of children's home and day care environments on their socioemotional development. Both in-home and out-of-home care experiences are assessed repeatedly during the course of the study. We hypothesize that either a positive home or day care environment can buffer children from one detrimental environment, and that particularly negative developmental effects will be found when both day care and home environments are of low quality or highly unstable. (5) To test the hypothesis that pre-enrollment designs in day care research yield less biased results than do designs in which families are recruited after decision about maternal employment and day care have been made.